Electron beam recording



July 13, 1965 N. R. NAIL v ELECTRON BEAM RECORDING Filed June 17, 1959 7 sin/mas FOR RECORD/M6 METAL SUPPORT VIEWER /POLAR/ZE/?$ I 9/ i %/2 NELSON R. IVA/L 6 INVENT OR. WM

ATTORNEYS United States Patent 3,lfi5,11tl ELECTRON BEAM RECORDING Nelson R. Nail, Rochester, N.Y., assignor to Eastman Kodak Company, Rochester, NY a corporation of New Jersey Filed June 17, 13 59, Ser. No. 821,023 9 Claims. (Cl. 340-173) This invention relates to a method of recording certain radiation energy. More particularly, thi invention concerns an improved method and apparatus arrangement for recording the energy from an electronic beam.

There are certain occasions in operations carried out in research and industry wherein it may be desired to make some type of a recording involving a source of radiation energy or impulses. One of the most common instances which has existed in the prior art has concerned the use of heat radiations such as those evolved from infrared, such infrared being caused to act upon a recording material. Many of the recording materials which have heretofore been used have comprised a paper or other fibrous base which carries a radiation sensitive coating on the surface. For example, such coatings have been made up of materials which will selectively melt or change at the point where the infrared energy is sufficiently intense. Other recording materials have comprised a chemical base which chemicals are changed by the radiation thereby producing an image or outline within or on the fibrous base. Such chemical change within or on the base may affect the fibrous composition of the recording medium thereby reducing the tensile strength thereof or rendering the fibrous recording medium unstable during storage. That is, such fibrous base recording materials which contain chemicals may fade or otherwise possess disadvantages because of the internal chemical action.

It is apparent, therefore, that the development of improved methods of recording radiation energy, particularly the energy delivered by an electronic beam represents a highly desirable result.

After extended investigation, I have found a method, improved recording materials and apparatus which is simpler, more economical and produces a better recording and otherwise is advantageous as compared with prior procedures.

One object of this invention is to provide an improved method for recording radiation impulses and the like. Another object is to provide a method which involves preparing a record on an uncoated, nonfibrous recording medium. Still another object is to provide a method of recording which does not materially alter the tensile strength or otherwise impair the recording film or sheet. Still a further object is to provide an apparatus assembly which is relatively simple and economical for recording and viewing the path of or image produced by the energy from an electronic beam. Other objects will appear hereinafter.

In the broader aspects of the present invention I have found that certain radiation impulses such as those emitted from an electron beam may be focused or otherwise caused to pass in contact with certain asymmetrically strained, transparent plastic sheets and a path or image will be formed in such sheets where the radiation energy contacts or passes through the sheet. In further detail, in an asymmetrically strained plastic sheet the molecular arrangement therein is in a certain predetermined direction. When the energy from the source of radiation is absorbed at a certain point or area in such sheet, this is sufficient to reduce the local strain and form an image which may be viewed in various ways. In other words, the energy from the electronic beam will alter the internal structure in the sheet at the point of contact of the energy 3,195,110 Patented July 13, 1965 thereby providing a means for tracing a path, outlining an image or otherwise recording the impulses in the strained plastic sheet. Since no chemical change is essen tial and inasmuch as an uncoated plastic film or sheet is used, the resultant recording is relatively permanent and substantially as strong as the original recording sheet. The superior strength, convenience of use and the like properties of the plastic film or sheet as compared with coated paper renders the present method of recording susceptible of use in apparatus wherein the plastic recording media may be in tape form and fed at high speeds through automatic equipment. The plastic tape carrying the recorded data as aforementioned may be automatically passed through viewing devices such as crossed polarizers as will be described in detail hereinafter.

For a further understanding of my invention reference will be made to the attached drawing forming a part of the resent application.

In the attached drawing:

E16. 1 is a diagrammatic side elevation view of an arrangement such as may be used to carry out my method;

FIG. 2 is a diagrammatic side elevation view illustrating one method of viewing the recording plastic tape of the present invention.

Referring to FIG. 1, a roll of asymmetrically strained film or sheeting in accordance with the present invention is shown at 2. Since this film while sensitive to certain types of energy is not sensitive to normal light, no special precautions need be taken for protecting the film prior to its exposure to the electron beam or other such source of energy, or during or after such exposure. This film is fed under an electronic beam diagrammatically indicated at 3, produced by electron gun 4. The film may be supported by plate means 5, which also serves to collect the electrons of the beam 3 after they have passed through and acted on the plastic sheet 2. As pointed out above, the electron beam acts on the asymmetrically strained film to record a path thereon. The electronic beam may be moved in any conventional manner across or up and down the film by means of a magnet appropriately positioned or by other devices such as deflection coils so placed as to control the position of the beam. The film with the recording thereon is then conducted to any storage or hold-up device generically designated 7. Here again, since the film of the present invention is substantially unaffected by normal atmospheric conditions, special facilities are not required for handling the film which has been thus exposed to an electronic beam.

It is, of course, understood that the means for generating the electronic beam will be enclosed in an appropriate evacuated vessel, not shown, that the plastic sheet 2 may be stored before and after use in the same vessel, or alternatively the strip of recording material may be led into and out of the evacuated vessel through appropriate air locks to allow storage before and after use under atmospheric conditions, or alternatively, that the means for generating the electron beam may be enclosed in an evacuated vessel and the electron beam 3 may emerge through a thin wall of the evacuated vessel into the atmosphere before impinging on the plastic sheet 2 which in this case can be wholly in the atmosphere.

If continuous operation is desired, provision may be made to feed the film with the recording directly to a viewer or reading means inasmuch as the images are recorded instantaneously in the asymmetrically strained film and no hold-up time is required for special treatment thereof prior to viewing.

Referring now to FIG. 2, the film or sheet 11 which now has some type of configuration therein due to the aforementioned exposure to a source of intense radiation which configuration is substantially permanently recorded thereon may be withdrawn as desired and passed between RC3 crossed polarizers 12 and 13 or other suitable means and the image, path or the like configurations thereon viewed by means of viewer 14 against the ground glass 15 illuminated by lamp 16.' The plastic film recording medium serves to rotate the beam of polarized light emanating from polarizer 12. I

In a preferred embodiment of my invention, the plane of polarizationproduced by the polarizer 12 is at 45 degreesto the axis of greatest strain in the plastic sheet. The polarizers 12 and 13 may be made up of tourmaline crystals, appropriately cut, or of Polaroid sheet polarizer manufactured by the Polaroid Corporation of Cambridge, Massachusetts.

The recording after viewing or other use thereof may be conducted to further storage means 17 or to other use. The viewer 14 may approximately consist of the eye of an observer or alternatively may consist of any photoresponsive element sensitive to the radiation effectively polarized by the polarizers I2 and 13. Filters may be inserted in the viewing arrangement to limit the spectral response of the system as required.

The asymmetrically strained tapes or films used herein preferably are prepared from polymeric sheeting such as polyethylene sheeting or polyester sheets. However, other transparent sheeting which may be asymmetrically strained exemplified by polyvinyl chloride sheeting and regenerated cellulose sheeting may be used in some instances. In'further detail, the transparent sheeting used in the present invention may comprise sheeting that has been formed by melting or otherwise liquefying the po lymer and extruding or otherwise forming the polymer into a thin sheet. This thin sheet is then drawn th ough drafting rolls or the like equipment so that the sheeting as originally formed is stretched one or more times either longitudinally or laterally. In general, it is preferred to stretch or strain the sheeting longitudinally as the most convenient way of obtaining an asymmetrically strained sheet. However, as indicated, film which is asymmetrically strained across the sheet likewise will function in the present invention.

In general, there is employed thermoplastic transparent film which has been asymmetrically strained at least 1%.

While it is preferred that the asymmetrically strained sheet that I use he strained in one direction at least several percent, in the broader aspects of the present invention a sheet which merely has been strained to a sufficient extent to be affected by the energy from radiation so that the energy reduces the local strain and produces some image in the plastic sheet is operative but the image may not be as good as in an optimum strained sheet.

Although this description has specified the use of crossed polarizers, it is also possible to practice this invention with parallel polarizers, or with polarizers set at any angle one to the other. The setting of the polarizers will determine the optimum amount of strain used in the plastic sheeting. In addition, rotation of either the analyzer or polarizer will convert the image observed from negative to positive.

It is well known in the art that if a monochromatically illuminated ground glass be viewed through crossed polarizers, lit=le or no light reaches the eye of the observer. The crossed polarizers effectively shut off the beam of light from the ground glass to the observers eye. If now, a homogeneous, transparent, unstrained plastic sheet be interposed between the polarizers, still little or no light reaches the observers eye. If, however, the plastic sheet be rendered birefringent by application of stress capable of producing a very small amount of asymmetrical strain, such as laterally stretching the plastic sheet at an angle of about 45 degrees to the plane of polarization determined by the polarizer, the field of view is seen to light up. With progressively greater amounts of stretching, the field cyclically lights up and darkens, the condition for a light field being that the optical retardation of the strained plastic sheet be an odd number of (g, half-wavelengths. When the sheet is. stretched to such a condition that the field has maximum brightness it is functioning as a half-wave plate. With very large amounts of stretching, in practice, the strains produced by the stretching become non-uniform and the field of view takes on a patterned appearance of light and dark areas.

If, with the field light, due to the presence between the polarizers of a suitably strained plastic sheet, either one of the polarizers be rotated 90 degrees it is found that the field is now dark, although if the sheet be removed, the field again becomes light. If nonmonochromatic light had been used in the above experiment, the changes observed would have included color changes as well as, in general, changes in brightness of the field of view.

Material suitable for the practice of this invention is made by stretching the plastic used until it contains, after release of the applied stress, such an amount of residual strain as to cause the field of view in the above-described experiment to appear light. There exist a number of optimal degrees of strain corresponding to the conditions causing each of the brightness maxima in the above experiment. Alternatively, the sheet may be grossly stretched to such a degree that the strains are no longer uniform on a microscopic scale. small areas over the entire sheet area will have the correct amount of strain birefringence to cause the field of view to appear light. The over-all appearance of the field will thus be light. Thus it is seen that the amount of stretching which is applied to the material in the practice of my invention may vary over certain limits. However, it is required for best operation that the transparent plastic sheet possess a proper degree of strain birefringence to cause the field to apepar light when the sheet is viewed between crossed polarizers set so that the direction of polarization makes an angle of about degrees with the axis of maximum strain in the plastic sheet. Or, if polarizers set at an angle of other than 90 degrees to each other be used for viewing, the plastic sheet should possess a proper degree of strain birefringence to cause,

I by its insertion between the polarizers, a distinct change in the brightness of the field. The amount of stretching which may be applied to achieve this condition with different plastic materials and different settings of the p0 larizers is seen to vary between substantial limits.

The preferred polyethylene sheeting used in this invention is made up of a polyethylene having a molecular Weight in the range of 5,000-200,000 and usually between 10,00050,000 and the resultant sheetingbeing of a thickness of 0.002 inch, which sheeting has been asymmetrically strained about 5%.

The polyester sheeting preferably used in the present method is made from a polyester as shown in Kibler et al. US. patent application Serial No. 554,639, now US. Patent No. 2,901,466. I

A further understanding of my invention will be had from a consideration of the following examples which are set forth for the purposes of illustrating certain preferred embodiments.

Example 1 In accordance with this example the recording media used comprised a film of polyethylene which had been stretched in one direction sufficient to produce asymmetry. This asymmetrically strained film was exposed to a 200 ,ua. 30 kv. electron beam of 4 mm. cross-section. This exposure was carried out in an apparatus arrangement similar to that illustrated in FIG. 1. After exposure in the area of the electron beam where the beam contacted the polyethylene sheeting, this reduced. the 10- cal strain and formed in the sheeting an image corre sponding to the path of the electron beam across the sheeting. The path of the electron beam on the sheeting was moved in various directions by means of a magnet which deflected the electronic beam. In this example the trace in this case,.

of the path of the electronic beam was produced at a rate of about two inches per second.

An immediate inspection of the sheet with the recording thereon through crossed polarizers showed that the path of the beam was cleanly marked and could be readily noted by such inspection. A check experiment proved that the eifect observed was not caused by heating, other than on a microscopic scale, of the plastic sheet.

Example II In accordance with this example, the same apparatus arrangement as used in the proceeding example and the same source of an electronic beam was used. However, the asymmetrically strained plastic sheet was essentially comprised of a polyester made up of aromatic acid reacted with a cyclohexane dimethanol. The path of the electronic beam was moved in various ways across the plastic sheet. Immediate observation of the plastic sheet after the exposure to the electronic beam just mentioned showed that a clear recording of the path of the electronic beam was incorporated into the sheeting. Again heating was not the cause of the observed eifect.

It is believed apparent from the foregoing that there has been provided a simple method for recording the energy from an electronic beam by absorbing such energy in an asymmetrically strained transparent film or sheet. The energy reduces the local strain in the sheet thereby forming an image that may be readily observed when the recording sheet is reviewed in a certain manner. Or, the recording may be fed through automatic equipment such as electronic computers and the recording used for any digital storage purpose.

Storage of these plastic tape recordings indicated that the strength of the plastic film had not been impaired.

The invention has been described in detail with par- 9 ticular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be eifected within the spirit and scope of the invention as described herein above and as defined in the appended claims.

I claim:

1. A method of recording the path of a beam from a source of radiation which comprises passing the beam into contact with asymmetrically strained uncoated plastic film the beam being passed in contact with the film to contact only portions thereof whereby the energy from the radiation where it contacts the film reduces the local strain and forms an observable image in the film and passing the film thus treated through a device whereby read-out may be accomplished.

2. A method in accordance with claim 1 wherein the film is exposed to an electron beam.

3. A method in accordance with claim 1 wherein the asymmertically strained film is essentially comprised of a polyolefin.

4. A method in accordance with claim 1 wherein the asymmetrically strained film is essentially comprised of a polyester composition.

5. A method in accordance with claim 1 wherein the asymmetrically strained film has been longitudinally drawn sufiicient to incorporate an amount of residual strain to cause the field of view in crossed polarizers to appear light.

6. A method in accordance with claim 1 wherein the film containing the image produced by the radiation is viewed through crossed polarizers.

7. As a new article of manufacture on uncoated film recording obtained from exposing an asymmetrically strained transparent plastic film to the energy from an electron beam the beam being passed in contact with the film to contact only portions thereof whereby the energy is absorbed at certain points in the film thereby reducing the local strain and forming the image therein.

8. A product in accordance with claim 7 wherein the film is essentially comprised of polyethylene.

9. A product in accordance with claim 7 wherein the film is essentially comprised of a polyester.

References Cited by the Examiner UNITED STATES PATENTS 2,707,162 4/55 Fries 1787.5 X 2,877,500 3/59 Rainer et a1 204-154 2,883,257 4/59 Wehe 346--74 2,904,700 9/59 Rockey 250219.1 2,923,198 2/60 Allen 88-14 FOREIGN PATENTS 384,258 12/32 Great Britain. 792,674 4/58 Great Britain.

IRVING L. SRAGOW, Primary Examiner. EVERETT R. REYNOLDS, Examiner. 

1. A METHOD OF RECORDING THE PATH OF A BEAM FROM A SOURCE OF RADIATION WHICH COMPRISES PASSING THE BEAM INTO CONTACT WITH ASYMMETRICALLY STRAINED UNCOATED PLASTIC FILM THE BEAM BEING PASSED IN CONTACT WITH THE FILM TO CONTACT ONLY PORTIONS THEREOF WHEREBY THE ENERGY FROM THE RADIATION WHERE IT CONTACTS THE FILM REDUCES THE LOCAL 